High water in Vicksburg: Another bridge strike, another breakaway
Pilot error was the primary cause of a bridge strike in Vicksburg, Miss., during high water in February 2019 that caused 30 grain barges to break away, according to federal investigators.
The 10,000-hp, twin-screw Chad Pregracke was downbound with its tow when at least one barge hit Pier 3 of the Old Highway 80 Bridge. The impact occurred at 0704 on Feb. 27 when the Lower Mississippi River was in flood stage. One barge sank and three others were damaged.
National Transportation Safety Board (NTSB) investigators determined that the pilot helming the 3-year-old vessel misjudged how the current would affect the tow after navigating around Delta Point, about a mile upriver from the bridge. The tow measured 210 feet wide and 1,173 feet long in a six-across, five-long configuration.
“Although the tow configuration and the pilot’s high-water experience met the Coast Guard’s recommended guidelines for mitigating the risk of a bridge strike, the pilot could not overcome the effect of the current on the tow,” the NTSB report said.
Marquette Transportation operates the towboat, which at the time of the incident was owned by the U.S. Bank National Association. The company did not respond to a request for comment.
The pilot at the helm was not identified. However, the NTSB said he had 18 years of experience operating tows on the Mississippi River and had developed a specialty working in high water. He passed through the Vicksburg bridges — the 89-year-old Old Highway 80 Bridge and the Interstate 20 Bridge — without incident two weeks earlier.
The bridges span an unusually challenging section of the Lower Mississippi. The passage is characterized by the 121-degree turn at Delta Point and the convergence of the Yazoo River, leading to cross-currents and eddies that change frequently. The Interstate 20 Bridge is located just downriver from the Old Highway 80 Bridge. Their piers align, creating an 820-foot-wide channel.
Conditions in this area are even more challenging in high water. The river gauge at Vicksburg measured 48 feet on the morning of the incident, with the current running at about 4.5 knots. Flood stage begins at 43 feet.
“The problem with this (section of river) is the current and being in close proximity to the Delta Point Bend,” Herman Smith, bridge commissioner for Warren County, Miss., told Professional Mariner in 2019. “These pilots know it, but the problem is the current is different almost every time they come down.”
Changing currents during high water greatly affect the approach to the Old Highway 80 Bridge and the Interstate 20 Bridge in Vicksburg, Miss.
Pat Rossi illustration
The Old Highway 80 Bridge carries railroad traffic between Mississippi and Louisiana just south of downtown Vicksburg. Historically, tows hit the bridge once or twice a year, although Smith said the frequency has gone up in recent years. There were five strikes in 2016, two in 2017, seven in 2018 and four in 2019. There has been one strike thus far in 2020, according to data Smith provided in early March.
“The higher the water, generally 34 feet and rising, the more chances we have of being struck by southbound tows,” he said in an email, noting that strikes also occur from northbound tows, albeit with less frequency.
Authorities and industry groups have recognized the challenges associated with the Vicksburg bridges for some time. Recent steps to address the issue include capping the number of loaded barges in a tow, requiring towboats to have certain horsepower ratings per barge, and limiting transits to daylight hours. The requirement called for 280 hp per barge at the time of the incident, but a week later the Coast Guard called for 300 hp for each barge in tow.
Two days before the incident, as the level of the Lower Mississippi rose, the Coast Guard reduced the number of loaded barges allowed to pass under the bridge to 30 from 36.
Chad Pregracke’s pilot pushed against the left descending bank at 0400 to await sunrise before passing under the two bridges. Before getting underway, the pilot discussed the transit with Marquette’s port captain. Chad Pregracke’s captain, who was on watch, did not have experience with high water in Vicksburg.
“The pilot stated that as the tow moved downriver, the current set the tow to the left side of the river despite his efforts to head toward the right side of the span,” the report said. “The pilot told investigators that he experienced the set to the left earlier and harder than he anticipated.”
The NTSB said the pivot point for the tow was roughly 400 feet from Chad Pregracke’s stern. That meant “the force acting on this smaller lever to steer the tow was not enough to overcome the force of the cross-currents acting on the larger lever of the tow.” Because of this, the current “turned the head of the tow and pushed it to port.”
The tow made contact on its port side between the third and fourth barges in the string, causing all 30 of the vessels to break away. None of the nine crewmembers aboard Chad Pregracke were injured.
The crew gathered the barges with help from other local towboats. Three damaged barges were taken to a local shipyard, and as of press time the sunken barge remained at the bottom of the river.